1. Field of the Invention
This invention relates to a method of manufacture of an active matrix substrate, on which are formed thin film transistors (TFTs), thin film diodes (TFDs), and other active elements in matrix form, as well as a method of manufacture of a liquid crystal display device using this active matrix substrate.
2. Description of the Related Art
Liquid crystal display devices, having a structure in which liquid crystals are enclosed between an active matrix substrate and an opposing substrate, are well-known. In such a liquid crystal display device, active elements and pixel electrodes to select and drive these elements are provided on the active matrix substrate, and an opposing electrode is provided on the opposing substrate. In order to effect color display in such a liquid crystal display device, a transmissive color filter, having red (R), green (G) and blue (B) tints, is arranged for individual display pixels.
In Japanese Patent Laid-open No. H9-292633, the formation of a color filter by imparting hardening ink to the aperture regions between TFTs formed on a substrate using an ink jet method, and the formation on this color filter of transparent pixel electrodes, are described.
However, in the Japanese Patent Laid-open No. H9-292633, formation of the ink layer and formation of the pixel electrodes must be performed separately, involving greater complexity in the manufacturing process.
In order to prevent the active element electrodes from being covered by ink jet discharge prior to formation of the pixel electrodes, the ink jet discharge must be performed after forming a passivation film and light-blocking layer on the entire upper surface of the active elements; however, contact holes must be formed in this passivation film and light-blocking layer for pixel electrodes connected to the active element electrodes, involving greater complexity in the manufacturing process.
On the other hand, in Japanese Patent Laid-open No. 8-313726, colored layers may be used as both a color filter and as pixel electrodes by making them conductive. By this means, formation of the ink layer and formation of the pixel electrodes can be performed in the same operation, and there is no longer a need to form contact holes in a passivation film and light-blocking layer.
However, in the Japanese Patent Laid-open No. H8-313726, patterning is performed by using a conductive resist as the color filter; however, the range of materials which can be selected in order to simultaneously satisfy the three requirements of optimal color adjustment, conductivity, and resist properties is extremely limited. For example, if an ordinary photopolymer-type color resist is mixed with conductive material, the occurrence of radicals due to the photoinitiator may be impeded, so that realization of such a material is difficult.
Also, because exposure, development, and other processes are indispensable for patterning using resist, complexity in the manufacturing process is unavoidable. And, patterning must be used to eliminate unnecessary resist, so that color materials and conductive materials are inevitably wasted.
An object of the present invention is to provide an active matrix substrate manufacturing method, and a method for manufacturing liquid crystal display devices using this active matrix substrate, which avoids such complexity in the manufacturing process, enables a broader range of material selection, and affords higher manufacturing yields.